The idea of ​​building a daring floating underground tunnel of Norway

The floating tunnel project running through these 7 bays is expected to reduce the time of driving between the two cities in Norway from 21 hours to 10.5 hours.

Previously, those who wanted to drive 680 miles from the bustling port of Kristiansand in southern Norway to Trondheim in the north had to sit in the car for up to 21 hours at an average speed of 30 miles per hour by the highway E39. It runs through 7 fjords, and cars must have up to 7 different ferries to get there.

But now, a new infrastructure project is being planned that promises to reduce travel time between the two locations to only 10.5 hours. This project will build fixed tunnel routes across all bays and is expected to be completed in 2035.

Because the creeks that travel on these bays are large and the largest part can be as deep as 1 mile, the construction of a normal bridge crossing is not feasible. That's why Norway is considering a route through the bays in an unprecedented way in the world: Floating underpass.

This is the term for a type of pipe located about 30 meters below the water surface but still a few hundred meters from the sea floor.

Advantages

This idea is not really impossible, as stated by Arianna Minoretti, a senior engineer in charge of infrastructure construction management. Originally intended, Sognefjord Bay was 1.3 km deep, more than 100 meters wide, possibly the first test site for this new floating tunnel. The project will consist of two circular concrete pipes for two lanes to be suspended at 18 to 30 meters below the water surface as shown below:

Sognefjord Bay may be the first place to test this new floating tunnel.

The pontoon bridges (red) on the water will keep these pipes balanced and the joints will match them together. This structure will also be attached to the stone floor below to increase certainty. Driving through here will feel like driving through any normal tunnel, simply driving when there is water on both the head and underfoot.

This design also offers many advantages compared to traditional methods, such as extreme weather does not affect the water as well as the structure below so the people here will rarely have to worry about congestion. Minoretti said: "This route will help people not to catch an entire helicopter to the hospital".

Previously, Norway had considered a plan to build a floating bridge across the bays but was in trouble that it might collide with some naval ships that sometimes exercise here or damage the beauty more or less. bay areas. Designing floating bunkers suspended in the water like this will solve both problems.

Building this floating tunnel system will not be too difficult as we first heard. Then Henry Petroski, a road and bridge engineer from Duke University, will use the concrete pouring technology for the latest tunnels and floating bridges as well as the construction of offshore oil platforms.

And above all, according to Minoretti, implementing this project is really interesting. The engineers will feel like surfing on the Discovery Channel every day.

Section of floating tunnel design in water.

However, there are still certain issues ahead. Nor are the Norwegians still seeking answers to some of the geological questions like the seabeds of the gulf actually look like? Or can the underground rocks below resist this floating tunnel project?

There are also other issues to consider, such as how far this floating tunnel can withstand the strong winds and waves or how the differences in flow between the 7 bays can affect tunnel design. Engineers are also investigating how the construction workers will maintain the work under the sea.

Although some people are still concerned about having to drive through an underwater tunnel, Norway actually has quite a bit of experience building underwater tunnels. Of the 1150 tunnels spread across the country, there were 35 tunnels running completely underwater.